[llvm] 077bff3 - [Analysis] isDereferenceableAndAlignedPointer(): recurse into select's hands

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2021-04-10T00:56:28+03:00
New Revision: 077bff39d46364035a5dcfa32fc69910ad0975d0

URL: https://github.com/llvm/llvm-project/commit/077bff39d46364035a5dcfa32fc69910ad0975d0
DIFF: https://github.com/llvm/llvm-project/commit/077bff39d46364035a5dcfa32fc69910ad0975d0.diff

LOG: [Analysis] isDereferenceableAndAlignedPointer(): recurse into select's hands

By doing this within the method itself,
we support traversing multiple levels of selects (TODO: PHI's),
fixing the SROA `std::clamp()` testcase.

Fixes https://bugs.llvm.org/show_bug.cgi?id=47271
Mostly fixes https://bugs.llvm.org/show_bug.cgi?id=49909

Added: 
    

Modified: 
    llvm/lib/Analysis/Loads.cpp
    llvm/test/Transforms/SROA/std-clamp.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp
index 8d01ea045097..2ae1fd5b5bde 100644
--- a/llvm/lib/Analysis/Loads.cpp
+++ b/llvm/lib/Analysis/Loads.cpp
@@ -59,6 +59,16 @@ static bool isDereferenceableAndAlignedPointer(
   // Note that it is not safe to speculate into a malloc'd region because
   // malloc may return null.
 
+  // Recurse into both hands of select.
+  if (const SelectInst *Sel = dyn_cast<SelectInst>(V)) {
+    return isDereferenceableAndAlignedPointer(Sel->getTrueValue(), Alignment,
+                                              Size, DL, CtxI, DT, TLI, Visited,
+                                              MaxDepth) &&
+           isDereferenceableAndAlignedPointer(Sel->getFalseValue(), Alignment,
+                                              Size, DL, CtxI, DT, TLI, Visited,
+                                              MaxDepth);
+  }
+
   // bitcast instructions are no-ops as far as dereferenceability is concerned.
   if (const BitCastOperator *BC = dyn_cast<BitCastOperator>(V)) {
     if (BC->getSrcTy()->isPointerTy())

diff  --git a/llvm/test/Transforms/SROA/std-clamp.ll b/llvm/test/Transforms/SROA/std-clamp.ll
index 561904252288..c0132a519722 100644
--- a/llvm/test/Transforms/SROA/std-clamp.ll
+++ b/llvm/test/Transforms/SROA/std-clamp.ll
@@ -6,18 +6,14 @@ target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16
 define float @_Z8stdclampfff(float %x, float %lo, float %hi) {
 ; CHECK-LABEL: @_Z8stdclampfff(
 ; CHECK-NEXT:  bb:
-; CHECK-NEXT:    [[I:%.*]] = alloca float, align 4
-; CHECK-NEXT:    [[I3:%.*]] = alloca float, align 4
 ; CHECK-NEXT:    [[I4:%.*]] = alloca float, align 4
-; CHECK-NEXT:    store float [[X:%.*]], float* [[I]], align 4
-; CHECK-NEXT:    store float [[LO:%.*]], float* [[I3]], align 4
 ; CHECK-NEXT:    store float [[HI:%.*]], float* [[I4]], align 4
-; CHECK-NEXT:    [[I5:%.*]] = fcmp fast olt float [[X]], [[LO]]
+; CHECK-NEXT:    [[I5:%.*]] = fcmp fast olt float [[X:%.*]], [[LO:%.*]]
 ; CHECK-NEXT:    [[I6:%.*]] = fcmp fast olt float [[HI]], [[X]]
-; CHECK-NEXT:    [[I7:%.*]] = select i1 [[I6]], float* [[I4]], float* [[I]]
-; CHECK-NEXT:    [[I8:%.*]] = select i1 [[I5]], float* [[I3]], float* [[I7]]
-; CHECK-NEXT:    [[I9:%.*]] = load float, float* [[I8]], align 4
-; CHECK-NEXT:    ret float [[I9]]
+; CHECK-NEXT:    [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATE_LOAD_TRUE:%.*]] = load float, float* [[I4]], align 4
+; CHECK-NEXT:    [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATED:%.*]] = select i1 [[I6]], float [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATE_LOAD_TRUE]], float [[X]]
+; CHECK-NEXT:    [[I9_SROA_SPECULATED:%.*]] = select i1 [[I5]], float [[LO]], float [[I9_SROA_SPECULATE_LOAD_FALSE_SROA_SPECULATED]]
+; CHECK-NEXT:    ret float [[I9_SROA_SPECULATED]]
 ;
 bb:
   %i = alloca float, align 4