diff --git a/clang/lib/Driver/ToolChains/AIX.h b/clang/lib/Driver/ToolChains/AIX.h
--- a/clang/lib/Driver/ToolChains/AIX.h
+++ b/clang/lib/Driver/ToolChains/AIX.h
@@ -16,10 +16,21 @@
 namespace driver {
 namespace tools {
 
-/// aix -- Directly call system default linker.
-// TODO: Enable direct call to system default assembler.
+/// aix -- Directly call system default assembler and linker.
 namespace aix {
 
+class LLVM_LIBRARY_VISIBILITY Assembler : public Tool {
+public:
+  Assembler(const ToolChain &TC) : Tool("aix::Assembler", "assembler", TC) {}
+
+  bool hasIntegratedCPP() const override { return false; }
+
+  void ConstructJob(Compilation &C, const JobAction &JA,
+                    const InputInfo &Output, const InputInfoList &Inputs,
+                    const llvm::opt::ArgList &TCArgs,
+                    const char *LinkingOutput) const override;
+};
+
 class LLVM_LIBRARY_VISIBILITY Linker : public Tool {
 public:
   Linker(const ToolChain &TC) : Tool("aix::Linker", "linker", TC) {}
@@ -53,6 +64,7 @@
   bool isPICDefaultForced() const override { return true; }
 
 protected:
+  Tool *buildAssembler() const override;
   Tool *buildLinker() const override;
 };
 
diff --git a/clang/lib/Driver/ToolChains/AIX.cpp b/clang/lib/Driver/ToolChains/AIX.cpp
--- a/clang/lib/Driver/ToolChains/AIX.cpp
+++ b/clang/lib/Driver/ToolChains/AIX.cpp
@@ -20,6 +20,61 @@
 
 using namespace llvm::opt;
 
+void aix::Assembler::ConstructJob(Compilation &C, const JobAction &JA,
+                                  const InputInfo &Output,
+                                  const InputInfoList &Inputs,
+                                  const ArgList &Args,
+                                  const char *LinkingOutput) const {
+  ArgStringList CmdArgs;
+
+  const bool IsArch32Bit = getToolChain().getTriple().isArch32Bit();
+  const bool IsArch64Bit = getToolChain().getTriple().isArch64Bit();
+  // Only support 32 and 64 bit.
+  if (!IsArch32Bit && !IsArch64Bit)
+    llvm_unreachable("Unsupported bit width value.");
+
+  // Specify the mode in which the as(1) command operates.
+  if (IsArch32Bit) {
+    CmdArgs.push_back("-a32");
+  } else {
+    // Must be 64-bit, otherwise asserted already.
+    CmdArgs.push_back("-a64");
+  }
+
+  // Accept an undefined symbol as an extern so that an error message is not
+  // displayed. Otherwise, undefined symbols are flagged with error messages.
+  // FIXME: This should be removed when the assembly generation from the
+  // compiler is able to write externs properly.
+  CmdArgs.push_back("-u");
+
+  // Accept any mixture of instructions.
+  // On Power for AIX and Linux, this behaviour matches that of GCC for both the
+  // user-provided assembly source case and the compiler-produced assembly
+  // source case. Yet XL with user-provided assembly source would not add this.
+  CmdArgs.push_back("-many");
+
+  Args.AddAllArgValues(CmdArgs, options::OPT_Wa_COMMA, options::OPT_Xassembler);
+
+  // Specify assembler output file.
+  assert((Output.isFilename() || Output.isNothing()) && "Invalid output.");
+  if (Output.isFilename()) {
+    CmdArgs.push_back("-o");
+    CmdArgs.push_back(Output.getFilename());
+  }
+
+  // Specify assembler input file.
+  // The system assembler on AIX takes exactly one input file.
+  if (Inputs.size() != 1)
+    llvm_unreachable("Invalid number of input files.");
+  const InputInfo &II = Inputs[0];
+  assert((II.isFilename() || II.isNothing()) && "Invalid input.");
+  if (II.isFilename())
+    CmdArgs.push_back(II.getFilename());
+
+  const char *Exec = Args.MakeArgString(getToolChain().GetProgramPath("as"));
+  C.addCommand(std::make_unique<Command>(JA, *this, Exec, CmdArgs, Inputs));
+}
+
 void aix::Linker::ConstructJob(Compilation &C, const JobAction &JA,
                                const InputInfo &Output,
                                const InputInfoList &Inputs, const ArgList &Args,
@@ -42,7 +97,7 @@
   if (Output.isFilename()) {
     CmdArgs.push_back("-o");
     CmdArgs.push_back(Output.getFilename());
-  } 
+  }
 
   // Set linking mode (i.e., 32/64-bit) and the address of
   // text and data sections based on arch bit width.
@@ -92,11 +147,12 @@
   C.addCommand(std::make_unique<Command>(JA, *this, Exec, CmdArgs, Inputs));
 }
 
-/// AIX - AIX tool chain which can call ld(1) directly.
-// TODO: Enable direct call to as(1).
+/// AIX - AIX tool chain which can call as(1) and ld(1) directly.
 AIX::AIX(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
     : ToolChain(D, Triple, Args) {
   getFilePaths().push_back(getDriver().SysRoot + "/usr/lib");
 }
 
+auto AIX::buildAssembler() const -> Tool * { return new aix::Assembler(*this); }
+
 auto AIX::buildLinker() const -> Tool * { return new aix::Linker(*this); }
diff --git a/clang/test/Driver/Inputs/aix_ppc_tree/dummy0.s b/clang/test/Driver/Inputs/aix_ppc_tree/dummy0.s
new file mode 100644
diff --git a/clang/test/Driver/Inputs/aix_ppc_tree/dummy1.s b/clang/test/Driver/Inputs/aix_ppc_tree/dummy1.s
new file mode 100644
diff --git a/clang/test/Driver/Inputs/aix_ppc_tree/dummy2.s b/clang/test/Driver/Inputs/aix_ppc_tree/dummy2.s
new file mode 100644
diff --git a/clang/test/Driver/aix-as.c b/clang/test/Driver/aix-as.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Driver/aix-as.c
@@ -0,0 +1,73 @@
+// General tests that as(1) invocations on AIX targets are sane. Note that we
+// only test assembler functionalities in this suite.
+
+// Check powerpc-ibm-aix7.1.0.0, 32-bit.
+// RUN: %clang -no-canonical-prefixes %s -### -c -o %t.o 2>&1 \
+// RUN:         -target powerpc-ibm-aix7.1.0.0 \
+// RUN:   | FileCheck --check-prefix=CHECK-AS32 %s
+// CHECK-AS32-NOT: warning:
+// CHECK-AS32: {{.*}}clang{{(.exe)?}}" "-cc1" "-triple" "powerpc-ibm-aix7.1.0.0"
+// CHECK-AS32: "{{.*}}as{{(.exe)?}}" 
+// CHECK-AS32: "-a32" 
+// CHECK-AS32: "-u" 
+// CHECK-AS32: "-many" 
+
+// Check powerpc64-ibm-aix7.1.0.0, 64-bit.
+// RUN: %clang -no-canonical-prefixes %s -### -c -o %t.o 2>&1 \
+// RUN:         -target powerpc64-ibm-aix7.1.0.0 \
+// RUN:   | FileCheck --check-prefix=CHECK-AS64 %s
+// CHECK-AS64-NOT: warning:
+// CHECK-AS64: {{.*}}clang{{(.exe)?}}" "-cc1" "-triple" "powerpc64-ibm-aix7.1.0.0"
+// CHECK-AS64: "{{.*}}as{{(.exe)?}}" 
+// CHECK-AS64: "-a64" 
+// CHECK-AS64: "-u" 
+// CHECK-AS64: "-many"
+
+
+// Check powerpc-ibm-aix7.1.0.0, 32-bit. -Xassembler <arg> option. 
+// RUN: %clang -no-canonical-prefixes %s -### -c -o %t.o 2>&1 \
+// RUN:         -Xassembler -w \
+// RUN:         -target powerpc-ibm-aix7.1.0.0 \
+// RUN:   | FileCheck --check-prefix=CHECK-AS32-Xassembler %s
+// CHECK-AS32-Xassembler-NOT: warning:
+// CHECK-AS32-Xassembler: {{.*}}clang{{(.exe)?}}" "-cc1" "-triple" "powerpc-ibm-aix7.1.0.0"
+// CHECK-AS32-Xassembler: "{{.*}}as{{(.exe)?}}" 
+// CHECK-AS32-Xassembler: "-a32" 
+// CHECK-AS32-Xassembler: "-u" 
+// CHECK-AS32-Xassembler: "-many"
+// CHECK-AS32-Xassembler: "-w"
+
+// Check powerpc64-ibm-aix7.1.0.0, 64-bit. -Wa,<arg>,<arg> option.
+// RUN: %clang -no-canonical-prefixes %s -### -c -o %t.o 2>&1 \
+// RUN:         -Wa,-v,-w \
+// RUN:         -target powerpc64-ibm-aix7.1.0.0 \
+// RUN:   | FileCheck --check-prefix=CHECK-AS64-Wa %s
+// CHECK-AS64-Wa-NOT: warning:
+// CHECK-AS64-Wa: {{.*}}clang{{(.exe)?}}" "-cc1" "-triple" "powerpc64-ibm-aix7.1.0.0"
+// CHECK-AS64-Wa: "{{.*}}as{{(.exe)?}}" 
+// CHECK-AS64-Wa: "-a64" 
+// CHECK-AS64-Wa: "-u" 
+// CHECK-AS64-Wa: "-many"
+// CHECK-AS64-Wa: "-v"
+// CHECK-AS64-Wa: "-w"
+
+// Check powerpc-ibm-aix7.1.0.0, 32-bit. Multiple input files.
+// RUN: %clang -no-canonical-prefixes -### -c \
+// RUN:         %S/Inputs/aix_ppc_tree/dummy0.s \
+// RUN:         %S/Inputs/aix_ppc_tree/dummy1.s \
+// RUN:         %S/Inputs/aix_ppc_tree/dummy2.s 2>&1 \
+// RUN:         -target powerpc-ibm-aix7.1.0.0 \
+// RUN:   | FileCheck --check-prefix=CHECK-AS32-MultiInput %s
+// CHECK-AS32-MultiInput-NOT: warning:
+// CHECK-AS32-MultiInput: "{{.*}}as{{(.exe)?}}"
+// CHECK-AS32-MultiInput: "-a32"
+// CHECK-AS32-MultiInput: "-u"
+// CHECK-AS32-MultiInput: "-many"
+// CHECK-AS32-MultiInput: "{{.*}}as{{(.exe)?}}"
+// CHECK-AS32-MultiInput: "-a32"
+// CHECK-AS32-MultiInput: "-u"
+// CHECK-AS32-MultiInput: "-many"
+// CHECK-AS32-MultiInput: "{{.*}}as{{(.exe)?}}"
+// CHECK-AS32-MultiInput: "-a32"
+// CHECK-AS32-MultiInput: "-u"
+// CHECK-AS32-MultiInput: "-many"