Allow isDereferenceablePointer to look through some bitcasts

isDereferenceablePointer should not give up upon encountering any bitcast. If
we're casting from a pointer to a larger type to a pointer to a small type, we
can continue by examining the bitcast's operand. This missing capability
was noted in a comment in the function.

In order for this to work, isDereferenceablePointer now takes an optional
DataLayout pointer (essentially all callers already had such a pointer
available). Most code uses isDereferenceablePointer though
isSafeToSpeculativelyExecute (which already took an optional DataLayout
pointer), and to enable the LICM test case, LICM needs to actually provide its DL
pointer to isSafeToSpeculativelyExecute (which it was not doing previously).

llvm-svn: 212686

1 files changed, 160 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LICM/hoist-bitcast-load.ll b/llvm/test/Transforms/LICM/hoist-bitcast-load.ll
new file mode 100644
index 00000000000..bb105e59edf
--- /dev/null
+++ b/llvm/test/Transforms/LICM/hoist-bitcast-load.ll
@@ -0,0 +1,160 @@
+; RUN: opt -S -basicaa -licm < %s | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Make sure the basic alloca pointer hoisting works:
+; CHECK-LABEL: @test1
+; CHECK: load i32* %c, align 4
+; CHECK: for.body:
+
+; Function Attrs: nounwind uwtable
+define void @test1(i32* nocapture %a, i32* nocapture readonly %b, i32 %n) #0 {
+entry:
+  %cmp6 = icmp sgt i32 %n, 0
+  %c = alloca i32
+  br i1 %cmp6, label %for.body, label %for.end
+
+for.body:                                         ; preds = %entry, %for.inc
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
+  %0 = load i32* %arrayidx, align 4
+  %cmp1 = icmp sgt i32 %0, 0
+  br i1 %cmp1, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  %1 = load i32* %c, align 4
+  %arrayidx3 = getelementptr inbounds i32* %b, i64 %indvars.iv
+  %2 = load i32* %arrayidx3, align 4
+  %mul = mul nsw i32 %2, %1
+  store i32 %mul, i32* %arrayidx, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}
+
+; Make sure the basic alloca pointer hoisting works through a bitcast to a
+; pointer to a smaller type:
+; CHECK-LABEL: @test2
+; CHECK: load i32* %c, align 4
+; CHECK: for.body:
+
+; Function Attrs: nounwind uwtable
+define void @test2(i32* nocapture %a, i32* nocapture readonly %b, i32 %n) #0 {
+entry:
+  %cmp6 = icmp sgt i32 %n, 0
+  %ca = alloca i64
+  %c = bitcast i64* %ca to i32*
+  br i1 %cmp6, label %for.body, label %for.end
+
+for.body:                                         ; preds = %entry, %for.inc
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
+  %0 = load i32* %arrayidx, align 4
+  %cmp1 = icmp sgt i32 %0, 0
+  br i1 %cmp1, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  %1 = load i32* %c, align 4
+  %arrayidx3 = getelementptr inbounds i32* %b, i64 %indvars.iv
+  %2 = load i32* %arrayidx3, align 4
+  %mul = mul nsw i32 %2, %1
+  store i32 %mul, i32* %arrayidx, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}
+
+; Make sure the basic alloca pointer hoisting works through a bitcast to a
+; pointer to a smaller type (where the bitcast also needs to be hoisted):
+; CHECK-LABEL: @test3
+; CHECK: load i32* %c, align 4
+; CHECK: for.body:
+
+; Function Attrs: nounwind uwtable
+define void @test3(i32* nocapture %a, i32* nocapture readonly %b, i32 %n) #0 {
+entry:
+  %cmp6 = icmp sgt i32 %n, 0
+  %ca = alloca i64
+  br i1 %cmp6, label %for.body, label %for.end
+
+for.body:                                         ; preds = %entry, %for.inc
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
+  %0 = load i32* %arrayidx, align 4
+  %cmp1 = icmp sgt i32 %0, 0
+  br i1 %cmp1, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  %c = bitcast i64* %ca to i32*
+  %1 = load i32* %c, align 4
+  %arrayidx3 = getelementptr inbounds i32* %b, i64 %indvars.iv
+  %2 = load i32* %arrayidx3, align 4
+  %mul = mul nsw i32 %2, %1
+  store i32 %mul, i32* %arrayidx, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}
+
+; Make sure the basic alloca pointer hoisting does not happen through a bitcast
+; to a pointer to a larger type:
+; CHECK-LABEL: @test4
+; CHECK: for.body:
+; CHECK: load i32* %c, align 4
+
+; Function Attrs: nounwind uwtable
+define void @test4(i32* nocapture %a, i32* nocapture readonly %b, i32 %n) #0 {
+entry:
+  %cmp6 = icmp sgt i32 %n, 0
+  %ca = alloca i16
+  %c = bitcast i16* %ca to i32*
+  br i1 %cmp6, label %for.body, label %for.end
+
+for.body:                                         ; preds = %entry, %for.inc
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
+  %0 = load i32* %arrayidx, align 4
+  %cmp1 = icmp sgt i32 %0, 0
+  br i1 %cmp1, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  %1 = load i32* %c, align 4
+  %arrayidx3 = getelementptr inbounds i32* %b, i64 %indvars.iv
+  %2 = load i32* %arrayidx3, align 4
+  %mul = mul nsw i32 %2, %1
+  store i32 %mul, i32* %arrayidx, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}
+
+attributes #0 = { nounwind uwtable }
+