From aa77513bb99775fb44eddea9ace0d45a55aaf802 Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Tue, 18 Dec 2018 22:54:03 +0000
Subject: [PATCH] Emit ASM input in a constant context

Summary:
Some ASM input constraints (e.g., "i" and "n") require immediate values. At O0,
very few code transformations are performed. So if we cannot resolve to an
immediate when emitting the ASM input we shouldn't delay its processing.

Reviewers: rsmith, efriedma

Reviewed By: efriedma

Subscribers: rehana, efriedma, craig.topper, jyknight, cfe-commits

Differential Revision: https://reviews.llvm.org/D55616

llvm-svn: 349561
---
 clang/lib/Basic/TargetInfo.cpp          |  2 ++
 clang/lib/CodeGen/CGStmt.cpp            |  7 +++++--
 clang/lib/Sema/SemaStmtAsm.cpp          | 16 ++++++++--------
 clang/test/CodeGen/builtin-constant-p.c | 11 +++++++++++
 4 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index 7b69cb097c84..269fad38b8d5 100644
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -685,7 +685,9 @@ bool TargetInfo::validateInputConstraint(
       // FIXME: Fail if % is used with the last operand.
       break;
     case 'i': // immediate integer.
+      break;
     case 'n': // immediate integer with a known value.
+      Info.setRequiresImmediate();
       break;
     case 'I':  // Various constant constraints with target-specific meanings.
     case 'J':
diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index bc7a18af1e5c..0242b48659d1 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -1820,11 +1820,14 @@ llvm::Value* CodeGenFunction::EmitAsmInput(
   // If this can't be a register or memory, i.e., has to be a constant
   // (immediate or symbolic), try to emit it as such.
   if (!Info.allowsRegister() && !Info.allowsMemory()) {
+    if (Info.requiresImmediateConstant()) {
+      llvm::APSInt AsmConst = InputExpr->EvaluateKnownConstInt(getContext());
+      return llvm::ConstantInt::get(getLLVMContext(), AsmConst);
+    }
+
     Expr::EvalResult Result;
     if (InputExpr->EvaluateAsInt(Result, getContext()))
       return llvm::ConstantInt::get(getLLVMContext(), Result.Val.getInt());
-    assert(!Info.requiresImmediateConstant() &&
-           "Required-immediate inlineasm arg isn't constant?");
   }
 
   if (Info.allowsRegister() || !Info.allowsMemory())
diff --git a/clang/lib/Sema/SemaStmtAsm.cpp b/clang/lib/Sema/SemaStmtAsm.cpp
index d209266049e6..b10b3d852c66 100644
--- a/clang/lib/Sema/SemaStmtAsm.cpp
+++ b/clang/lib/Sema/SemaStmtAsm.cpp
@@ -378,17 +378,17 @@ StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
                          << InputExpr->getSourceRange());
     } else if (Info.requiresImmediateConstant() && !Info.allowsRegister()) {
       if (!InputExpr->isValueDependent()) {
-        Expr::EvalResult EVResult;
-        if (!InputExpr->EvaluateAsInt(EVResult, Context))
+        llvm::SmallVector<PartialDiagnosticAt, 1> Diags;
+        llvm::APSInt Result = InputExpr->EvaluateKnownConstInt(Context, &Diags);
+        if (!Diags.empty())
           return StmtError(
               Diag(InputExpr->getBeginLoc(), diag::err_asm_immediate_expected)
               << Info.getConstraintStr() << InputExpr->getSourceRange());
-        llvm::APSInt Result = EVResult.Val.getInt();
-         if (!Info.isValidAsmImmediate(Result))
-           return StmtError(Diag(InputExpr->getBeginLoc(),
-                                 diag::err_invalid_asm_value_for_constraint)
-                            << Result.toString(10) << Info.getConstraintStr()
-                            << InputExpr->getSourceRange());
+        if (!Info.isValidAsmImmediate(Result))
+          return StmtError(Diag(InputExpr->getBeginLoc(),
+                                diag::err_invalid_asm_value_for_constraint)
+                           << Result.toString(10) << Info.getConstraintStr()
+                           << InputExpr->getSourceRange());
       }
 
     } else {
diff --git a/clang/test/CodeGen/builtin-constant-p.c b/clang/test/CodeGen/builtin-constant-p.c
index 7f4e7d07cc66..f1cd06ad4aab 100644
--- a/clang/test/CodeGen/builtin-constant-p.c
+++ b/clang/test/CodeGen/builtin-constant-p.c
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s -O2 | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s -O0 | FileCheck --check-prefix=O0 %s
 
 int a = 42;
 
@@ -166,3 +167,13 @@ struct { const char *t; int a; } test15[] = {
 
 extern char test16_v;
 struct { int a; } test16 = { __builtin_constant_p(test16_v) };
+
+extern unsigned long long test17_v;
+
+void test17() {
+  // O0: define void @test17
+  // O0: call void asm sideeffect "", {{.*}}(i32 -1) 
+  // CHECK: define void @test17
+  // CHECK: call void asm sideeffect "", {{.*}}(i32 -1) 
+  __asm__ __volatile__("" :: "n"( (__builtin_constant_p(test17_v) || 0) ? 1 : -1));
+}
-- 
2.34.1