[llvm] 0372768 - [InstCombine] Simplify calls with "returned" attribute
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Fri Mar 20 02:23:49 PDT 2020
Author: Nikita Popov
Date: 2020-03-20T10:23:39+01:00
New Revision: 03727687766a72504712861bf038f0be962527d0
URL: https://github.com/llvm/llvm-project/commit/03727687766a72504712861bf038f0be962527d0
DIFF: https://github.com/llvm/llvm-project/commit/03727687766a72504712861bf038f0be962527d0.diff
LOG: [InstCombine] Simplify calls with "returned" attribute
If a call argument has the "returned" attribute, we can simplify
the call to the value of that argument. This was already partially
handled by InstSimplify/InstCombine for the case where the argument
is an integer constant, and the result is thus known via known bits.
The non-constant (or non-int) argument cases weren't handled though.
This previously landed as an InstSimplify transform, but was reverted
due to assertion failures when compiling the Linux kernel. The reason
is that simplifying a call to another call breaks assumptions in
call graph updating during inlining. As the code is not easy to fix,
and there is no particularly strong motivation for having this in
InstSimplify, the transform is only performed in InstCombine instead.
Differential Revision: https://reviews.llvm.org/D75815
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
llvm/test/Transforms/InstCombine/align-attr.ll
llvm/test/Transforms/InstCombine/call-returned.ll
llvm/test/Transforms/InstCombine/expensive-combines.ll
llvm/test/Transforms/InstCombine/fortify-folding.ll
llvm/test/Transforms/InstCombine/strcpy_chk-1.ll
llvm/test/Transforms/InstCombine/strncpy_chk-1.ll
llvm/test/Transforms/InstCombine/unused-nonnull.ll
llvm/test/Transforms/InstSimplify/call.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 38c7a95f90dd..e0a35e74adbd 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -4566,6 +4566,10 @@ Instruction *InstCombiner::visitCallBase(CallBase &Call) {
if (I) return eraseInstFromFunction(*I);
}
+ if (!Call.use_empty() && !Call.isMustTailCall())
+ if (Value *ReturnedArg = Call.getReturnedArgOperand())
+ return replaceInstUsesWith(Call, ReturnedArg);
+
if (isAllocLikeFn(&Call, &TLI))
return visitAllocSite(Call);
diff --git a/llvm/test/Transforms/InstCombine/align-attr.ll b/llvm/test/Transforms/InstCombine/align-attr.ll
index 16782dba2eff..2b004311cc8e 100644
--- a/llvm/test/Transforms/InstCombine/align-attr.ll
+++ b/llvm/test/Transforms/InstCombine/align-attr.ll
@@ -20,7 +20,7 @@ define i32 @foo2(i32* align 32 %a) #0 {
; CHECK-LABEL: @foo2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[V:%.*]] = call i32* @func1(i32* [[A:%.*]])
-; CHECK-NEXT: [[TMP0:%.*]] = load i32, i32* [[V]], align 32
+; CHECK-NEXT: [[TMP0:%.*]] = load i32, i32* [[A]], align 32
; CHECK-NEXT: ret i32 [[TMP0]]
;
entry:
diff --git a/llvm/test/Transforms/InstCombine/call-returned.ll b/llvm/test/Transforms/InstCombine/call-returned.ll
index 6fc20079671b..fb0a6462db79 100644
--- a/llvm/test/Transforms/InstCombine/call-returned.ll
+++ b/llvm/test/Transforms/InstCombine/call-returned.ll
@@ -17,7 +17,7 @@ define i32 @returned_const_int_arg() {
define i8* @returned_const_ptr_arg() {
; CHECK-LABEL: @returned_const_ptr_arg(
; CHECK-NEXT: [[X:%.*]] = call i8* @passthru_p8(i8* null)
-; CHECK-NEXT: ret i8* [[X]]
+; CHECK-NEXT: ret i8* null
;
%x = call i8* @passthru_p8(i8* null)
ret i8* %x
@@ -26,7 +26,7 @@ define i8* @returned_const_ptr_arg() {
define i32 @returned_var_arg(i32 %arg) {
; CHECK-LABEL: @returned_var_arg(
; CHECK-NEXT: [[X:%.*]] = call i32 @passthru_i32(i32 [[ARG:%.*]])
-; CHECK-NEXT: ret i32 [[X]]
+; CHECK-NEXT: ret i32 [[ARG]]
;
%x = call i32 @passthru_i32(i32 %arg)
ret i32 %x
diff --git a/llvm/test/Transforms/InstCombine/expensive-combines.ll b/llvm/test/Transforms/InstCombine/expensive-combines.ll
index 28acb773bfd5..96a45b05cfb5 100644
--- a/llvm/test/Transforms/InstCombine/expensive-combines.ll
+++ b/llvm/test/Transforms/InstCombine/expensive-combines.ll
@@ -16,7 +16,7 @@ define void @test() {
;
; EXPENSIVE-OFF-LABEL: @test(
; EXPENSIVE-OFF-NEXT: [[CALL:%.*]] = call i32 @passthru(i32 0)
-; EXPENSIVE-OFF-NEXT: call void @sink(i32 [[CALL]])
+; EXPENSIVE-OFF-NEXT: call void @sink(i32 0)
; EXPENSIVE-OFF-NEXT: ret void
;
%call = call i32 @passthru(i32 0)
diff --git a/llvm/test/Transforms/InstCombine/fortify-folding.ll b/llvm/test/Transforms/InstCombine/fortify-folding.ll
index ee81557615a5..b2171a44f57e 100644
--- a/llvm/test/Transforms/InstCombine/fortify-folding.ll
+++ b/llvm/test/Transforms/InstCombine/fortify-folding.ll
@@ -82,7 +82,7 @@ define i32 @test_not_sprintf() {
define i8* @test_strcat() {
; CHECK-LABEL: @test_strcat(
; CHECK-NEXT: [[STRCAT:%.*]] = call i8* @strcat(i8* nonnull dereferenceable(1) getelementptr inbounds ([60 x i8], [60 x i8]* @a, i64 0, i64 0), i8* nonnull dereferenceable(1) getelementptr inbounds ([60 x i8], [60 x i8]* @b, i64 0, i64 0))
-; CHECK-NEXT: ret i8* [[STRCAT]]
+; CHECK-NEXT: ret i8* getelementptr inbounds ([60 x i8], [60 x i8]* @a, i64 0, i64 0)
;
%dst = getelementptr inbounds [60 x i8], [60 x i8]* @a, i32 0, i32 0
%src = getelementptr inbounds [60 x i8], [60 x i8]* @b, i32 0, i32 0
@@ -126,7 +126,7 @@ define i64 @test_not_strlcat() {
define i8* @test_strncat() {
; CHECK-LABEL: @test_strncat(
; CHECK-NEXT: [[STRNCAT:%.*]] = call i8* @strncat(i8* nonnull dereferenceable(1) getelementptr inbounds ([60 x i8], [60 x i8]* @a, i64 0, i64 0), i8* nonnull dereferenceable(1) getelementptr inbounds ([60 x i8], [60 x i8]* @b, i64 0, i64 0), i64 22)
-; CHECK-NEXT: ret i8* [[STRNCAT]]
+; CHECK-NEXT: ret i8* getelementptr inbounds ([60 x i8], [60 x i8]* @a, i64 0, i64 0)
;
%dst = getelementptr inbounds [60 x i8], [60 x i8]* @a, i32 0, i32 0
%src = getelementptr inbounds [60 x i8], [60 x i8]* @b, i32 0, i32 0
diff --git a/llvm/test/Transforms/InstCombine/strcpy_chk-1.ll b/llvm/test/Transforms/InstCombine/strcpy_chk-1.ll
index 02a4b5cbdeac..67e393d1525b 100644
--- a/llvm/test/Transforms/InstCombine/strcpy_chk-1.ll
+++ b/llvm/test/Transforms/InstCombine/strcpy_chk-1.ll
@@ -53,7 +53,7 @@ define i8* @test_simplify3() {
define i8* @test_simplify4() {
; CHECK-LABEL: @test_simplify4(
; CHECK-NEXT: [[STRCPY:%.*]] = call i8* @strcpy(i8* nonnull dereferenceable(1) getelementptr inbounds ([60 x i8], [60 x i8]* @a, i32 0, i32 0), i8* nonnull dereferenceable(1) getelementptr inbounds ([60 x i8], [60 x i8]* @b, i32 0, i32 0))
-; CHECK-NEXT: ret i8* [[STRCPY]]
+; CHECK-NEXT: ret i8* getelementptr inbounds ([60 x i8], [60 x i8]* @a, i32 0, i32 0)
;
%dst = getelementptr inbounds [60 x i8], [60 x i8]* @a, i32 0, i32 0
%src = getelementptr inbounds [60 x i8], [60 x i8]* @b, i32 0, i32 0
diff --git a/llvm/test/Transforms/InstCombine/strncpy_chk-1.ll b/llvm/test/Transforms/InstCombine/strncpy_chk-1.ll
index ed90303b2808..7601b1669359 100644
--- a/llvm/test/Transforms/InstCombine/strncpy_chk-1.ll
+++ b/llvm/test/Transforms/InstCombine/strncpy_chk-1.ll
@@ -39,7 +39,7 @@ define i8* @test_simplify2() {
define i8* @test_simplify3() {
; CHECK-LABEL: @test_simplify3(
; CHECK-NEXT: [[STRNCPY:%.*]] = call i8* @strncpy(i8* nonnull dereferenceable(1) getelementptr inbounds ([60 x i8], [60 x i8]* @a, i32 0, i32 0), i8* nonnull dereferenceable(1) getelementptr inbounds ([60 x i8], [60 x i8]* @b, i32 0, i32 0), i32 12)
-; CHECK-NEXT: ret i8* [[STRNCPY]]
+; CHECK-NEXT: ret i8* getelementptr inbounds ([60 x i8], [60 x i8]* @a, i32 0, i32 0)
;
%dst = getelementptr inbounds [60 x i8], [60 x i8]* @a, i32 0, i32 0
%src = getelementptr inbounds [60 x i8], [60 x i8]* @b, i32 0, i32 0
diff --git a/llvm/test/Transforms/InstCombine/unused-nonnull.ll b/llvm/test/Transforms/InstCombine/unused-nonnull.ll
index 0a1520ea73c2..382d2634b86c 100644
--- a/llvm/test/Transforms/InstCombine/unused-nonnull.ll
+++ b/llvm/test/Transforms/InstCombine/unused-nonnull.ll
@@ -12,13 +12,8 @@ define i32 @main(i32 %argc, i8** %argv) #0 {
; CHECK-SAME: (i32 [[ARGC:%.*]], i8** nocapture readnone [[ARGV:%.*]]) local_unnamed_addr #0
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = icmp slt i32 [[ARGC]], 2
-; CHECK-NEXT: br i1 [[TMP0]], label [[DONE:%.*]], label [[DO_WORK:%.*]]
-; CHECK: do_work:
-; CHECK-NEXT: [[TMP1:%.*]] = tail call i32 @compute(i8* undef, i32 [[ARGC]])
-; CHECK-NEXT: br label [[DONE]]
-; CHECK: done:
-; CHECK-NEXT: [[RETVAL:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[TMP1]], [[DO_WORK]] ]
-; CHECK-NEXT: ret i32 [[RETVAL]]
+; CHECK-NEXT: [[SPEC_SELECT:%.*]] = select i1 [[TMP0]], i32 0, i32 [[ARGC]]
+; CHECK-NEXT: ret i32 [[SPEC_SELECT]]
;
entry:
%0 = getelementptr inbounds i8*, i8** %argv, i32 0
diff --git a/llvm/test/Transforms/InstSimplify/call.ll b/llvm/test/Transforms/InstSimplify/call.ll
index 108de9082a70..07fdcdbbd5e6 100644
--- a/llvm/test/Transforms/InstSimplify/call.ll
+++ b/llvm/test/Transforms/InstSimplify/call.ll
@@ -978,6 +978,10 @@ define <2 x double> @negated_mag_arg_vec(<2 x double> %x) {
ret <2 x double> %r
}
+; We handle the "returned" attribute only in InstCombine, because the fact
+; that this simplification may replace one call with another may cause issues
+; for call graph passes.
+
declare i32 @passthru_i32(i32 returned)
declare i8* @passthru_p8(i8* returned)
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