Use Alias Analysis to hoist 2 loads from diamond to the common predecessor basic block.

Alias Analysis allows to detect real barriers for load hoisting.

Review in http://reviews.llvm.org/D5991

llvm-svn: 221091

1 files changed, 64 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstMerge/ld_hoist1.ll b/llvm/test/Transforms/InstMerge/ld_hoist1.ll
new file mode 100644
index 00000000000..715f1b82440
--- /dev/null
+++ b/llvm/test/Transforms/InstMerge/ld_hoist1.ll
@@ -0,0 +1,64 @@
+; Test load hoist
+; RUN: opt -basicaa -memdep -mldst-motion -S < %s | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc_linux"
+
+; Function Attrs: nounwind uwtable
+define float* @foo(i32* noalias nocapture readonly %in, float* noalias %out, i32 %size, i32* nocapture readonly %trigger)  {
+entry:
+  %cmp11 = icmp eq i32 %size, 0
+  br i1 %cmp11, label %for.end, label %for.body.lr.ph
+
+for.body.lr.ph:                                   ; preds = %entry
+  %0 = add i32 %size, -1
+  br label %for.body
+
+; CHECK-LABEL: for.body
+; CHECK: load
+; CHECK:  %2 = getelementptr inbounds i32* %in, i64 %indvars.iv
+; CHECK:  %3 = load i32* %2, align 4
+
+for.body:                                         ; preds = %for.body.lr.ph, %for.inc
+  %indvars.iv = phi i64 [ 0, %for.body.lr.ph ], [ %indvars.iv.next, %for.inc ]
+  %arrayidx = getelementptr inbounds i32* %trigger, i64 %indvars.iv
+  %1 = load i32* %arrayidx, align 4
+  %cmp1 = icmp sgt i32 %1, 0
+  br i1 %cmp1, label %if.then, label %if.else
+
+; CHECK-LABEL: if.then
+if.then:                                          ; preds = %for.body
+; This load should be hoisted
+  %arrayidx3 = getelementptr inbounds i32* %in, i64 %indvars.iv
+  %2 = load i32* %arrayidx3, align 4
+  %conv = sitofp i32 %2 to float
+  %add = fadd float %conv, 5.000000e-01
+  %arrayidx5 = getelementptr inbounds float* %out, i64 %indvars.iv
+  store float %add, float* %arrayidx5, align 4
+  br label %for.inc
+
+if.else:                                          ; preds = %for.body
+  %arrayidx7 = getelementptr inbounds float* %out, i64 %indvars.iv
+  %3 = load float* %arrayidx7, align 4
+  %div = fdiv float %3, 3.000000e+00
+  store float %div, float* %arrayidx7, align 4
+; This load should be hoisted in spite of store 
+  %arrayidx9 = getelementptr inbounds i32* %in, i64 %indvars.iv
+  %4 = load i32* %arrayidx9, align 4
+  %conv10 = sitofp i32 %4 to float
+  %add13 = fadd float %div, %conv10
+  store float %add13, float* %arrayidx7, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.then, %if.else
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv to i32
+  %exitcond = icmp ne i32 %lftr.wideiv, %0
+  br i1 %exitcond, label %for.body, label %for.cond.for.end_crit_edge
+
+for.cond.for.end_crit_edge:                       ; preds = %for.inc
+  br label %for.end
+
+for.end:                                          ; preds = %entry, %for.cond.for.end_crit_edge
+  ret float* %out
+}
+