3b2011fd4f
When the IV is only used by the terminating condition (say IV-A) and the loop has a predictable back-edge count and we have another IV (say IV-B) that is an affine add recursion, we will be able to calculate the terminating value of IV-B in the loop pre-header. This patch adds attempts to replace IV-B as the new terminating condition and remove IV-A. It is safe to do so since IV-A is only used as the terminating condition. This transformation is suitable to be appended after LSR as it may optimize the loop into the situation mentioned above. The transformation can reduce number of IV-s in the loop by one. A cli option `lsr-term-fold` is added and default disabled. Reviewed By: mcberg2021, craig.topper Differential Revision: https://reviews.llvm.org/D132443
161 lines
6.2 KiB
LLVM
161 lines
6.2 KiB
LLVM
; REQUIRES: asserts
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; RUN: opt < %s -passes="loop-reduce" -S -debug -lsr-term-fold 2>&1 | FileCheck %s
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target datalayout = "e-p:32:32:32-n32"
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define i32 @loop_variant(ptr %ar, i32 %n, i32 %m) {
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; CHECK: Cannot fold on backedge that is loop variant
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entry:
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br label %for.cond
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for.cond: ; preds = %for.cond, %entry
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%n.addr.0 = phi i32 [ %n, %entry ], [ %mul, %for.cond ]
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%cmp = icmp slt i32 %n.addr.0, %m
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%mul = shl nsw i32 %n.addr.0, 1
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br i1 %cmp, label %for.cond, label %for.end
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for.end: ; preds = %for.cond
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ret i32 %n.addr.0
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}
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define i32 @nested_loop(ptr %ar, i32 %n, i32 %m, i32 %o) {
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; CHECK: Cannot fold on backedge that is loop variant
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; CHECK: Cannot fold on non-innermost loop
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entry:
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%cmp15 = icmp sgt i32 %o, 0
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br i1 %cmp15, label %for.body, label %for.cond.cleanup
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for.cond.cleanup: ; preds = %for.cond.cleanup3, %entry
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%cnt.0.lcssa = phi i32 [ 0, %entry ], [ %cnt.1.lcssa, %for.cond.cleanup3 ]
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ret i32 %cnt.0.lcssa
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for.body: ; preds = %entry, %for.cond.cleanup3
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%i.017 = phi i32 [ %inc6, %for.cond.cleanup3 ], [ 0, %entry ]
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%cnt.016 = phi i32 [ %cnt.1.lcssa, %for.cond.cleanup3 ], [ 0, %entry ]
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%sub = sub nsw i32 %n, %i.017
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%cmp212 = icmp slt i32 %sub, %m
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br i1 %cmp212, label %for.body4, label %for.cond.cleanup3
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for.cond.cleanup3: ; preds = %for.body4, %for.body
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%cnt.1.lcssa = phi i32 [ %cnt.016, %for.body ], [ %inc, %for.body4 ]
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%inc6 = add nuw nsw i32 %i.017, 1
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%cmp = icmp slt i32 %inc6, %o
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br i1 %cmp, label %for.body, label %for.cond.cleanup
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for.body4: ; preds = %for.body, %for.body4
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%j.014 = phi i32 [ %mul, %for.body4 ], [ %sub, %for.body ]
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%cnt.113 = phi i32 [ %inc, %for.body4 ], [ %cnt.016, %for.body ]
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%inc = add nsw i32 %cnt.113, 1
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%mul = shl nsw i32 %j.014, 1
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%cmp2 = icmp slt i32 %mul, %m
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br i1 %cmp2, label %for.body4, label %for.cond.cleanup3
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}
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; The terminating condition folding transformation cannot find the ptr IV
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; because it checks if the value comes from the LoopPreheader. %mark is from
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; the function argument, so it is not qualified for the transformation.
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define void @no_iv_to_help(ptr %mark, i32 signext %length) {
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; CHECK: Cannot find other AddRec IV to help folding
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entry:
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%tobool.not3 = icmp eq i32 %length, 0
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br i1 %tobool.not3, label %for.cond.cleanup, label %for.body
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for.cond.cleanup: ; preds = %for.body, %entry
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ret void
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for.body: ; preds = %entry, %for.body
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%i.05 = phi i32 [ %dec, %for.body ], [ %length, %entry ]
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%dst.04 = phi ptr [ %incdec.ptr, %for.body ], [ %mark, %entry ]
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%0 = load ptr, ptr %dst.04, align 8
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call ptr @foo(ptr %0)
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%incdec.ptr = getelementptr inbounds ptr, ptr %dst.04, i64 1
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%dec = add nsw i32 %i.05, -1
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%tobool.not = icmp eq i32 %dec, 0
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br i1 %tobool.not, label %for.cond.cleanup, label %for.body
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}
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declare void @foo(ptr)
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define void @NonAddRecIV(ptr %a) {
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; CHECK: SCEV of phi ' %lsr.iv = phi i32 [ %lsr.iv.next, %for.body ], [ 1, %entry ]'
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; CHECK: is not an affine add recursion, not qualified for the terminating condition folding.
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entry:
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%uglygep = getelementptr i8, ptr %a, i32 84
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%lsr.iv1 = phi ptr [ %uglygep2, %for.body ], [ %uglygep, %entry ]
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%lsr.iv = phi i32 [ %lsr.iv.next, %for.body ], [ 1, %entry ]
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store i32 1, ptr %lsr.iv1, align 4
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%lsr.iv.next = mul nsw i32 %lsr.iv, 2
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%uglygep2 = getelementptr i8, ptr %lsr.iv1, i64 4
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%exitcond.not = icmp eq i32 %lsr.iv.next, 65536
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br i1 %exitcond.not, label %for.end, label %for.body
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for.end: ; preds = %for.body
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ret void
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}
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@fp_inc = common global float 0.000000e+00, align 4
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define void @NonSCEVableIV(float %init, float* %A, i32 %N) {
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; CHECK: IV of phi ' %x.05 = phi float [ %init, %entry ], [ %add, %for.body ]'
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; CHECK: is not SCEV-able, not qualified for the terminating condition folding.
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entry:
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%0 = load float, float* @fp_inc, align 4
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br label %for.body
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for.body: ; preds = %entry
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%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
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%x.05 = phi float [ %init, %entry ], [ %add, %for.body ]
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%arrayidx = getelementptr inbounds float, float* %A, i64 %indvars.iv
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store float %x.05, float* %arrayidx, align 4
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%add = fsub float %x.05, %0
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%lftr.wideiv = trunc i64 %indvars.iv.next to i32
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%exitcond = icmp eq i32 %lftr.wideiv, %N
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br i1 %exitcond, label %for.end, label %for.body
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for.end: ; preds = %for.end
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ret void
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}
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define void @NonIcmpEqNe(ptr %a) {
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; CHECK: Cannot fold on branching condition that is not an ICmpInst::eq / ICmpInst::ne
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entry:
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%uglygep = getelementptr i8, ptr %a, i64 84
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%lsr.iv1 = phi ptr [ %uglygep2, %for.body ], [ %uglygep, %entry ]
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%lsr.iv = phi i64 [ %lsr.iv.next, %for.body ], [ 379, %entry ]
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store i32 1, ptr %lsr.iv1, align 4
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%lsr.iv.next = add nsw i64 %lsr.iv, -1
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%uglygep2 = getelementptr i8, ptr %lsr.iv1, i64 4
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%exitcond.not = icmp sle i64 %lsr.iv.next, 0
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br i1 %exitcond.not, label %for.end, label %for.body
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for.end: ; preds = %for.body
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ret void
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}
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define void @TermCondMoreThanOneUse(ptr %a) {
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;CHECK: Cannot replace terminating condition with more than one use
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entry:
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%uglygep = getelementptr i8, ptr %a, i64 84
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%lsr.iv1 = phi ptr [ %uglygep2, %for.body ], [ %uglygep, %entry ]
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%lsr.iv = phi i64 [ %lsr.iv.next, %for.body ], [ 379, %entry ]
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store i32 1, ptr %lsr.iv1, align 4
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%lsr.iv.next = add nsw i64 %lsr.iv, -1
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%uglygep2 = getelementptr i8, ptr %lsr.iv1, i64 4
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%exitcond.not = icmp eq i64 %lsr.iv.next, 0
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%dummy = select i1 %exitcond.not, i8 0, i8 1
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br i1 %exitcond.not, label %for.end, label %for.body
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for.end: ; preds = %for.body
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ret void
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}
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